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March 21, 2011, 10:02 |
Problem with simpleFoam
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#1 |
Member
Join Date: Oct 2010
Location: Naples
Posts: 50
Rep Power: 15 |
Dear foamers, i have a problem.
Every time I do a calculation with simpleFoam, I have problems related to the type of mesh used. In fact, using an airfoil, if I use a fairly low number of cells as 20,000 I get acceptable results, but if my airfoil is thicker (70000) of the cells i have completely absurd results : the solution diverges. I do not change anything between the various settings, change only the mesh. could you tell me if there is a parameter that should be changed depending on the quality of the mesh?? |
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March 21, 2011, 11:22 |
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#2 | |
Senior Member
Mirko Vukovic
Join Date: Mar 2009
Posts: 159
Rep Power: 17 |
Quote:
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March 22, 2011, 05:41 |
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#3 |
Member
Join Date: Oct 2010
Location: Naples
Posts: 50
Rep Power: 15 |
Hello,
I use the cam to calculate the Co courant in openFoam? |
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March 22, 2011, 06:15 |
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#4 | |
Senior Member
maddalena
Join Date: Mar 2009
Posts: 436
Rep Power: 23 |
Quote:
Salvo, could you post checkMesh of the old (coarse) mesh and the new (finest) mesh? How do you made the refinement? Increasing the cell number does not mean that you improve mesh quality!!! What about y+ values? Have you try to see where the problem may be using simpleFoamResiduals? mad |
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March 22, 2011, 10:23 |
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#5 |
Member
Join Date: Oct 2010
Location: Naples
Posts: 50
Rep Power: 15 |
hi maddalena,sorry for my english.
i put in the terminal Co so i have the Courant number for my mesh. I have a very very high value of this number:6*10^6. i think that this is the problem for my case. i know that i can impose Co=1 knowing the distance between cells and the time step. How can I calculate these factors for my mesh???I don't know how calcolate the distance between cells thanks |
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March 22, 2011, 17:01 |
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#6 | |
Senior Member
maddalena
Join Date: Mar 2009
Posts: 436
Rep Power: 23 |
Hi Salvo,
Quote:
However... are you really using simpleFoam? If so, than Co has no meaning at all! See equation 2.2 here In your case you should have set deltaT=1, since simpleFoam is a steady state solver, thus deltaT is an iteration counter only! If you want, delete the maxCo line in controlDict file. simpleFoam should no complain about this missing entry, since it does not need it. In conclusion: the problem lies somewhere else... mad |
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March 23, 2011, 03:54 |
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#7 |
Member
Join Date: Oct 2010
Location: Naples
Posts: 50
Rep Power: 15 |
thank you for yor help, maddalena. i decided to re-make the mesh!!!
just a curiosity, are you italian?? |
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March 23, 2011, 03:56 |
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#8 |
Senior Member
maddalena
Join Date: Mar 2009
Posts: 436
Rep Power: 23 |
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